The long-term goal of the lab is to understand how organisms maintain their genomic information at the molecular level. We are investigating one of the ways genomes can be altered in a process called transposition. Transposons are mobile DNA elements that can move within a cell which are found in nearly every organism and are abundant in the human genome. To better understand transposition at the molecular level we are using the bacterial transposon Tn7. Tn7 transposition is of particular interest in that it also allows us to understand DNA replication and repair because Tn7 recognizes complexes involved in these processes as insertion targets. This work is related to human health because it will lead to a better understanding of cellular DNA repair functions found in all living organisms that are important in preventing cancer. Tn7 is able to recognize a structure or complex associated with multiple forms of DNA metabolism using the Tn7-encoded protein TnsE. TnsE-mediated transposition preferentially occurs into plasmids capable of moving between cells called conjugal plasmids. The TnsE-mediated pathway also recognizes structures associated with the repair of DNA double-strand breaks and allows Tn7 to preferentially direct transposition where DNA replication terminates. We will determine if TnsE interacts directly with the beta-clamp processivity factor to recognize lagging- strand DNA replication. We will determine how the TnsE protein interacts with a target DNA and core machinery to recruit the rest of the transposition apparatus. The transposition pathway will be established in a reconstituted in vitro reaction to understand the mechanism of target site selection at the molecular level. Relevance to Public Health: We will use a highly tractable bacterial system to get a better understanding of how DNA replication and repair function. This will provide much needed insight into very similar systems in humans which when non-functional can lead to cancer. Public health will be served because a better understanding of DNA repair and replication provides insight into the genesis of cancer.